1. Technical Field
The present invention relates to an illumination device, a coordinate inputting device, an electro-optical device, and an electronic apparatus, and more particularly, to a configuration of an illumination device that is very appropriate to be used in a display device having an optical position detecting unit.
2. Related Art
Generally, in display devices having an electro-optical device such as a liquid crystal display body, in order to allow a display screen to be visually recognized or increase the visibility, an illumination device such as a back light is frequently used. In addition, in the display devices, a pointed position detecting unit such as a touch panel may be disposed in a display screen. In such a case, by pointing a specific spot in the display screen with a pen, a finger, or the like, the pointed position is detected so as to be input to an information processing apparatus or the like.
As a pointed position detection unit (a position coordinate inputting unit) such as the touch panel, an electrostatic capacitance-type touch panel, a resistance film-type touch panel, or the like for mechanically or electrically detecting the state of a contact on the display screen have been known. In addition, other than the above-described touch panels, optical touch panels that can detect positional coordinates of a finger or the like for a case where infrared rays are blocked with the finger or the like, for example, by running a plurality of the infrared rays horizontally and vertically along the display screen and disposing light detectors corresponding thereto for detecting the infrared rays have been known. Generally, various types of optical touch panels have been known. For example, there are touch panels disclosed in JP-A-2004-295644 and JP-A-2004-303172.
However, in the above-described optical touch panels, a plurality of light sources and light detectors, a plurality of light switches, or a plurality of light guiding structures corresponding to resolution of positional coordinates to be detected in the vicinity of the display screen is needed to be arranged. Accordingly, the structure becomes complicated, and the number of optical elements is increased. As a result, there is a problem that a high manufacturing cost incurs.
In addition, by preparing the above-described complicated structure, the thickness of the device is increased or the external dimension of the device may be increased for a case where the structure is disposed on the outer peripheral side for preventing the increase of the thickness of the device.